1. Field of the Disclosure
Embodiments disclosed herein relate generally to systems and methods for handling and disposing of drill cuttings from drilling operations. Specifically, embodiments disclosed herein relate to a cuttings transfer system for transferring drill cuttings discharged by a separator.
2. Background Art
Oilfield drilling fluid, often called “mud,” serves multiple purposes in the industry. Among its many functions, the drilling mud acts as a lubricant to cool rotary drill bits and facilitate faster cutting rates. Typically, the mud is mixed at the surface and pumped downhole at high pressure to the drill bit through a bore of the drillstring. Once the mud reaches the drill bit, it exits through various nozzles and ports where it lubricates and cools the drill bit. After exiting through the nozzles, the “spent” fluid returns to the surface through an annulus formed between the drillstring and the drilled wellbore.
Furthermore, drilling mud provides a column of hydrostatic pressure, or head, to prevent “blow out” of the well being drilled. This hydrostatic pressure offsets formation pressures, thereby preventing fluids from blowing out if pressurized deposits in the formation are breached. Two factors contributing to the hydrostatic pressure of the drilling mud column are the height (or depth) of the column (i.e., the vertical distance from the surface to the bottom of the wellbore) itself and the density (or its inverse, specific gravity) of the fluid used. Depending on the type and construction of the formation to be drilled, various weighting and lubrication agents are mixed into the drilling mud to obtain the right mixture. Typically, drilling mud weight is reported in “pounds,” short for pounds per gallon. Generally, increasing the amount of weighting agent solute dissolved in the mud base will create a heavier drilling mud. Drilling mud that is too light may not protect the formation from blow outs, and drilling mud that is too heavy may over invade the formation. Therefore, much time and consideration is spent to ensure the mud mixture is optimal. Because the mud evaluation and mixture process is time consuming and expensive, drillers and service companies prefer to reclaim the returned drilling mud and recycle it for continued use.
Another significant purpose of the drilling mud, which is also known as drilling fluid, is to carry the cuttings away from the drill bit at the bottom of the borehole to the surface. As a drill bit pulverizes or scrapes the rock formation at the bottom of the borehole, small pieces of solid material are left behind. The drilling fluid exiting the nozzles at the bit acts to stir-up and carry the solid particles of rock and formation to the surface within the annulus between the drillstring and the borehole. Therefore, the fluid exiting the borehole from the annulus is a slurry of formation cuttings in drilling fluid. Before the fluid can be recycled and re-pumped down through nozzles of the drill bit, the cuttings must be removed.
Apparatus in use today to remove cuttings from drilling fluid are commonly referred to in the industry as shale shakers or vibratory separators. A vibratory separator is a vibrating sieve-like table upon which returning solids laden drilling fluid is deposited and through which clean drilling fluid emerges. Typically, the vibratory separator is an angled table with a generally perforated filter screen bottom. Returning drilling fluid is deposited at the feed end of the vibratory separator. As the drilling fluid travels down the length of the vibrating table, the fluid falls through the perforations to a reservoir below, leaving the cuttings or solid particulates behind. The vibrating action of the vibratory separator table conveys cuttings left behind to a discharge end of the separator table. The cuttings may be oil based or water based. If they are water based cuttings they are usually discarded with out further treatment. If they are oil based cuttings they may have to be transported to another cleaning process. Typically, the transportation of cuttings away from the separator is accomplished by a mechanical auger, also known as a screw conveyor. The mechanical auger includes a tube and a helical shaped shaft. The helical shaped shaft is contained within the tube and configured to rotate. While the helical shaft rotates, it forces the cuttings to move in single direction, thereby transporting the cuttings through the tube.
Accordingly, there exists a need for a cuttings transfer system that transfers cuttings in a safe and efficient manner.